The Gustave Roussy Child Pain Scale (Douleur Enfant Gustave Roussy, DEGR(R)Scale) is a scale for grading prolonged pain in children aged 2-6 years with cancer. The scale comprised six behaviours specific to pain items, five psychomotor inertia items, and four anxiety items, with a total score ranging from 0 to 60. This work was designed to confirm the scale structure and to study its construct validity and convergent validity.Our work was composed of two parts. In the first part of the study, 152 children with progressive cancer were scored by two nurses using the DEGR(R)scale, in a cross-sectional design. And in the second part, 53 of these 152 children were video-recorded. The tapes were assessed both by a panel of four pain specialists using a 0 to 7 Likert scale and by a nurse using DEGR(R)scale.As for the 152 children, the mean of the total scores derived from the DEGR(R)is 20.2 (SD = 6.2). Both the degree of agreement between the nurses (the weighted kappa coefficient) and the internal consistency of the scale (Cronbach alpha coefficient = 0.90) were high, providing evidence of good reliability. Multivariate factor analyses showed a first factor of intensity of pain (51% of the total variance) and a second factor (14% of the total variance) which distinguishes the psychomotor inertia items from the items concerning voluntary expression of pain. Also, the results showed that psychomotor inertia items contribute to both factors and that it is an important sign of prolonged pain. Construct validity was strengthened by the absence of correlation between DEGR(R)scores and variables not related to pain, including fever, neutropenia and anaemia (indicative of poor medical condition) and the absence of parents' visits (indicative of psychological distress).Concerning the 53 video-recorded children, the nurses' DEGR(R)ratings were strongly correlated with the specialists panel scores indicating a fairly good case for convergent validity. Copyright 1999 European Federation of Chapters of the International Association for the Study of Pain.